What is the legitimate way to return the house to my sister after I wrote it in my name, knowing that she will inherit from me, and her parents do not hold the country's nationality?

If the sister gifted the house and registered it in the questioner's name while she was not in her death illness, and the house was possessed, then the gift is complete and it has become his property.

Since the sister is an heir, a bequest to her is not valid. However, it is permissible for the questioner to gift the house back to her during his lifetime. This is not considered a prohibited revocation of the gift, as some jurists allow the donor to re-possess his previous gift from the donee through a gift, purchase, or charity.